I would persevere with slackening the cables as much as possible and rotating and pulling the disc to get it off rather than forcing it to snap the springs. The reason I say that is I tried to do the same thing myself once and rather than the spring failing it pulled the spring locating plate off the brake back plate. Fortunately I was able to weld it back on to effect a good repair - in the absence of a small welder you would have to replace the backplate itself.
Note also that to remove the spings, you need to compress them and rotate them until the small amount of metal at the top which attaches the centre rod to the spring is horizontal - then slide the spring on the horizontal in the direction of that small piece of metal - i.e. if it's at 9 o'clock then to the left, if it's at 3 o'clock then to the right.
You will see what I mean when you look at them :
https://www.ebay.co.uk/p/Volvo-30645...3707089&chn=ps